A finisher 100 includes a pair of bundle discharge rollers 130, a lower stack tray 137, and a width-direction aligning portion 200. The width-direction aligning portion includes a pair of aligning members 1 and a driving motor. The aligning member includes a pair of first aligning members 91 that is rotatably supported while being movable in the sheet width direction orthogonal to the discharge direction and a pair of second aligning members 92. The driving motor rotates the pair of first aligning members and moves the pair of first aligning members in the width direction. When the pair of first aligning members rotates and one of the pair of second aligning members abuts on the sheet, the pair of second aligning members forms opposite surfaces in which the sheet can be aligned in the width direction, and the pair of first aligning members align the sheet by the opposite surfaces.